During some manufacturing processes, manufacturers sometimes apply a chemical which is a protective coating to their product to protect its surface during their product manufacturing process. This protective coating stays on until their product is ready to be shipped from their factory. That protective coating is only a temporary protective coating on the product substrate because that protective coating must be removed toward or at the end of the manufacturing process in an effective manner. This technique is particularly practiced in the aviation industry wherein a protective coating is applied to some exterior and some interior of parts during the early stages of manufacturing of an aircraft. The coating must later be effectively removed prior to a painting stage to avoid fisheyes in a high polished and painted surface.
In other industries, the material is used in service. For example, such protecting chemical is a polysulfide based material, usually sold with an activator. The polysulfide-based material is applied to the metal part after premixing with a recommended amount of activator, for example, and the polysulfide cured for a time to provide the protective sealant.
In other instances, one may simply desire to remove a chemical of some kind from a substrate containing that chemical on its surface simply because a different chemical is desired to be placed upon a cleaned substrate or perhaps that user does not desire to apply a second chemical over a first chemical on that substrate. In all cases, the effective removal of a chemical residing on the surface of the substrate from the surface in a manner which does not harm the substrate is desired. In some instances, a user will have a tougher chemical removal task as he will wish to remove one or more layers of chemicals on the surface of a substrate. In some instances, that removal task is more daunting as the user may have a substrate which has at least one layer of a chemical resident on the surface of a substrate for a period of years.
Several U.S. patents describe prior art processes and compositions for removal of chemicals from surfaces.
For example, U.S. Pat. No. 5,413,729 discloses a composition used to remove coating from substrates comprising at least one lactone and at least one ester. This composition is reported to optionally contain water, aromatic solvents, organic solvents, surfactants, thickeners, corrosion inhibitors, fragrances and/or other additives (see col. 3, lines 7-12). Esters can be dibasic acid esters (col. 3, lines 44-55). This composition is reported to be applied easily, level out and have the ability to cling to vertical surfaces as disclosed in column 4, lines 27-44. Column 3, lines 63-68 of this patent discloses that adding water to the composition unexpectedly results in little reduction in the overall effectiveness of the lactone/ester composition. While Example 6 discloses a composition that does not have water present, this patent clearly teaches that it is advantageous to use water in the composition of the patent.
U.S. Pat. No. 4,927,556 discloses a composition containing at least one dibasic ester (both dimethyl and diethyl esters are suitable), water and at least one thickening agent (col. 1, line 67- col 2, line 5). The amount of water required is at least 55% by weight (col. 2, lines 15-16). Thickening agents which must be soluble in water or swellable in water allow the composition to be applied easily, level out and have the ability to cling to vertical surfaces are disclosed in column 3, lines 17-32. This patent discloses that, while the dibasic esters are known to be capable of removing paint by themselves, their lower viscosities rend them unsuitable for use on vertical surfaces (col, 4, lines 1-3). This patent also discloses that the presence of water allows the expensive dibasic esters to be used as a paint remover (col. 4, lines 15-17). This patent teaches away from using non-aqueous compositions.
Canadian Patent 2,122,879 discloses a method for removing coating films from surfaces by pressure spraying a chemical stripping composition onto the surface, allowing the stripping composition to strip the coating from the surface, and removing the mixture of stripping composition and coating by applying a vacuum. The stripping composition can be a composition comprising NMP, d-limonene, dimethyl glutarate, dimethyl adipate, dimethyl succinate, and the remaining consisting of a surfactant. This patent discloses that the stripping compositions needs to be of such a consistency so as to coat surfaces with minimal runs and drips, i.e., the compositions need to be modified with a bonding agent such as hydroxyethyl cellulose.
This use of water in the above-reported compositions is not acceptable for many substrates including metals and wood, and is also believed to be a major factor in causing hydrolysis of the dimethyl ester, an undesirable situation. For many situations, water is unacceptable because of its corrosion potential. A thickened, non-aqueous dibasic ester composition which effectively removes chemicals from such substances is highly desirable. There is a high desirability to replace materials highly volatile, toxic materials such as MEK (methyl ethyl ketone), 111 -trichlorethane and the like.